Donald Trump has campaigned to repeal and replace the Affordable Care Act, otherwise known as Obamacare, once he gets into office. Now that he's won the presidency with a majority Republican House and Senate, that feat might not prove to be too easy. Wonkblog's Max Ehrenfreund explains. (Daron Taylor/The Washington Post)

While it's pretty much a given that the Affordable Care Act won't survive a Trump presidency and Republican Congress in its current form, there are sweeping implications of reversing a law that has reached in so many ways into our health care system. The government has never undone a major benefits program after it has taken effect — and neither the incoming administration nor GOP lawmakers know exactly how they'll replace it.

If your head is spinning because of the politics and lingo that's being thrown around, here's a primer on what we know about the president-elect's plans so far and what they might mean for the ACA marketplaces and for you personally.

Let's start at the beginning. What did Donald Trump promise on the campaign trail?

As a candidate, Trump released a plan, “Healthcare Reform to Make America Great Again,” which called for a full repeal of Obama's signature domestic achievement on “day one” of the new administration. You can read the original text here. He later said he would call Congress into special session to repeal the law. Now that he has been elected president, Trump's timeline is unclear. Most of what he wants to do requires an act of Congress.

GOP leaders on Capitol Hill say that ending the ACA is a priority for them, too. But lawmakers' aides have not yet begun to compare notes with the president-elect and his transition team on substance or strategy.

What has he said on the subject since the election?

Last week Trump created a stir by saying he might “amend” the ACA instead of repealing and replacing it. But his views on the substance of the law didn't change. As he'd said during his campaign, he mentioned keeping the provision that forbids insurers to deny coverage to people with preexisting medical problems. He also said he'd like to continue letting young adults stay on their parents' insurance policies until they are 26 — an idea that has been part of House Republicans' health-care plan.

On Sunday, Trump talked about the ACA during an interview on CBS's "60 Minutes” with reporter Lesley Stahl. Repealing and replacing the law would be done “simultaneously,” he explained, so that people would not face a limbo period with no insurance.

“It’ll be better health care, much better, for less money,” he promised. “Not a bad combination.”

Trump has revised other health-care positions to conform more closely to the heart of Republican thinking in recent decades. On his presidential transition site, GreatAgain.gov, he has added antiabortion statements and several policy positions that were not part of his campaign’s platform as well as deleted a few proposals. A Washington Post story that ran several days after the election detailed some of the changes.

Post reporter Amy Goldstein walks us through what changes health care will face under a Trump presidency. President-elect Donald Trump campaigned on his promise to repeal and replace the Affordable Care Act. (The Washington Post)

If Congress and the Trump White House repeal the ACA, how soon would my marketplace health plan go away?

It's hard to know, but there are some clues. Early this year, when lawmakers sent Obama an ACA-repeal bill, which they knew he wouldn't sign, they included in the legislation a two-year period before the marketplaces and other parts of the law ceased.

Right now, the fourth year's open enrollment for marketplace health plans is underway. The plans that consumers can buy until Jan. 31 have pledged to participate through 2017. More than eight in 10 ACA customers receive federal subsidies to help pay for their premiums, and it is unlikely that those will go away as soon as Trump takes office. According to the Health and Human Services Department, just over 1 million people chose ACA health plans during the first 12 days of this month, about 50,000 more than the same period a year ago. That puts enrollment roughly on pace to match the 1.6 million who signed up during the first three weeks of the last enrollment period. HHS officials said that sign-ups increased during the three days after the election.

I have a 23-year-old son without a full-time job. Will he lose his coverage through my insurance plan?

This is unclear — but might not change. After the election, Trump began to say that he likes the ACA provision that lets young adults stay on their parents' policy until they are 26. House Republicans support this idea, too.

I'm being bombarded with messages on social media urging me to get an IUD before coverage for birth control disappears. How seriously should I take this? Will I lose really lose that benefit?

I have truly never been more shocked in my life. Hug your friends a little tighter, promise to protect each other, & everyone go get an IUD

In the 24 to 48 hours following the election, it was hard to ignore panic about birth control. Cosmo magazine reported that “Women Are Urging Each Other to Get IUDs Now — Before It's Too Late,” and Quartz warned that “a Trump presidency will threaten women’s reproductive rights.” Many commentators raised the idea of women getting an IUD, a intrauterine device type of birth control that is reversible but long-lasting, noting that it could get them through an entire presidential term.

For the past six years under the ACA, women have had access to free birth control through their insurance plans because of a provision requiring coverage for preventive health benefits. Trump hasn't addressed this issue, but fears have been stoked because he became more clearly opposed to abortion as the campaign went on. And Vice President-elect Mike Pence is a strong social conservative who opposes abortion in almost all circumstances.

Technically speaking, Trump might not even have to rely on Congress to get rid of these benefits. HHS could redefine what types of services must be included among the preventive care the law requires insurers to provide. For more details on this, check out Vox's explainer.

That's not very reassuring. What about coverage for other benefits we have now? Should I stock up on the medicine I have to take regularly for diabetes, arthritis or other chronic diseases or conditions?

Feeling anxious about the upcoming changes is understandable because they will likely be pretty big. But doctors recommend against hoarding prescription drugs. Even if the law or federal rules change, it may take a little time to figure out exactly what has happened. When the ACA was passed, patient groups months combed through the documentation for months before figuring out that HIV drugs, for example, weren't covered adequately in some cases.

Marketplace guide Jim Prim works on Healthcare.gov as he helps a Delaware resident sign up for coverage under the Affordable Care Act in 2014. (Andrew Harrer/Bloomberg)

Will the ACA insurance exchanges go away? If so, where would people who don’t get insurance through an employer obtain coverage?

Trump has not provided a lot of details. Again, Congress's last attempt to repeal the ACA would have had a two-year transition period. And remember, for all the attention they get, marketplace health plans are covering about 11 million people — a small fraction of the approximately 214 million people with any kind of private health insurance at last count by the U.S. Census.

What will happen to health insurance prices?

This is a big debate among economists. To understand why this question is so difficult to answer, you have to look at the recent history of health plan prices before and after the ACA. Before, premiums purchased by individuals were rising about 10 percent per year — but because insurers were able to deny coverage to sick people, they were able to keep overall costs down. That changed when the law required companies to insure everyone.

In 2014, the first year of the insurance exchanges, analyses showed that prices for certain benchmark plans were 10 to 20 percent cheaper than before the law took effect. Prices have climbed since then, but liberal and conservative economists have argued over whether the increases were more or less than what would have happened without the ACA. An important point to keep in mind is that most people who buy in an ACA market get subsidies. Trump has not detailed whether he would offer similar assistance or whether his tax proposals would end up saving people more than under Obamacare.

I’m getting a monthly subsidy that lowers the premium of my ACA plan. What will happen to this subsidy?

The law's subsidies might go away. Under some Republican thinking, you and other consumers might be able to make up part of the money by deducting the premiums from your taxes. But critics say that would not help lower-income people, who do not pay much, if any, in taxes.

I’m finishing college and deciding where to move. Which states are most likely to have affordable health care for people with low-paying jobs in the next few years — and which are least likely?

This is a tough one as we're still in the early stages of postelection discussion on what will replace the ACA. If you need to make an immediate decision, it's worth looking at how certain states have historically dealt with the issue of health insurance. Massachusetts has been at the forefront of offering universal access to health care for years and would probably still be a good bet. The state implemented its own version of the ACA several years before the federal law took effect nationally; that will remain in place even if the ACA goes away. It might also be helpful to look at states that set up their own insurance exchanges and expanded their Medicaid programs under the ACA. While your low-paying job may or may not meet the Medicaid threshold, the overall trend in these states is toward more people being covered (though it is uncertain if those states would continue to get extra federal money for their Medicaid beneficiaries).

Below is a map of the 19 states that opted against Medicaid expansion. The list, from the Kaiser Family Foundation, was current as of October.

Since Trump keeps saying he wants to replace the ACA, what are his main ideas and where do they come from? Have they ever been tried before?

Taking away health insurance from about 20 million people — which would happen if the ACA were repealed with no replacement — would be wildly unpopular, and Trump has outlined several parts of a possible successor plan. Some of the ideas come from legislation that was introduced in recent years by congressional Republicans, including House Speaker Paul Ryan, but has never become law. The major changes Trump has endorsed, often without details, include:

allowing medications to be imported, creating more competition in drug pricing. (This shows up on Trump's campaign page but not on his transition page.)

Give me the high-level numbers. What would be the impact of Trump's positions on insurance marketplaces and the economy?

Most analyses agree that many more people would be uninsured but differ on how the federal deficit would be affected. According to Rand Corp., in the first full year of the new administration, Trump’s proposals would result in about 20 million previously insured Americans going without health coverage and would add nearly $6 billion to the deficit.

(Rand Corp.)

In contrast, the Center for Health and Economy, which is nonpartisan and includes both liberal and conservative experts, estimates that 18 million people — mostly low-income adults — would become uninsured in the first year and that Trump's changes would decrease the deficit by $583 billion between 2017 and 2026.

Previously, the Committee for a Responsible Federal Budget, which promotes fiscal constraint and is anti-deficit, calculated that repealing the ACA would double the number of uninsured, leading to more than 21 million people losing coverage, and would cost $550 billion over a decade.

The Congressional Budget Office in 2015 estimated 22 million fewer people would have coverage in 2017 if a repeal bill were enacted.

Tell me more about making Medicaid a block-grant program for states. What does that mean, and what difference would that probably make?

Since it began in the mid-1960s, Medicaid has been an entitlement program, which means that it is an open-ended commitment to cover everyone who qualifies for it. In return, states must cover certain groups of people and certain benefits, though they have some freedom to include or exclude some discretionary benefits and to set eligibility rules. The result is that federal spending on Medicaid varies from year to year, depending on how many people are in the program and how much care they use. In contrast, under a block grant, the government would give states a lump sum of money. Kaiser Health News has a good explanation of how this would work.

Critics say that, over time, a lot of money would be cut from Medicaid if the federal grants fail to keep pace with the program's costs, inevitably eroding eligibility and benefits.

Yet supporters say block grants would encourage states to reduce waste, save the federal government billions of dollars and give states more freedom to choose how to implement the program. Oren Cass, a senior fellow at the Manhattan Institute, block grants can be done in a way that would satisfy both sides. Speaking to Politico, Cass said that savings from implementing the grants could then be used for other anti-poverty programs.

Another looming question is what will happen with the part of the ACA intended to expand Medicaid eligibility to people with slightly higher incomes — up to 138 percent of the federal poverty level, which this year is about $16,000 for an individual and $33,000 for a family of four. Thirty-one states and the District did expansion. It is unclear whether, in making other changes to Medicaid, Trump would let them keep the extra federal money they received for enrolling newly eligible people.

Lena H. Sun and Lenny Bernstein contributed to this report.

Have questions about the Affordable Care Act under the Trump administration? Please submit your questions to healthlaw@washpost.com.